Twelve people were killed, and multiple people were injured after a mass shooting at a Southern California bar late Wednesday.

About 40 miles west of Los Angeles, a gunman opened fire inside a country western dance bar. At least 11 victims were killed and a deputy died from his injuries, said Ventura County Sheriff Geoff Dean. The gunman was found dead inside.

The bar was hosting an event for college students at the time.

"There is blood everywhere," Dean said Thursday morning.

This is the deadliest mass shooting in the United States since 17 students and teachers were killed at a Parkland, Florida, school in February.